implement better-auth auth with postgres and route protection

app/api/watchlist/[id]/route.ts

@@ -1,4 +1,5 @@
 import { jsonError } from '@/lib/server/http';
+import { requireAuthenticatedSession } from '@/lib/server/auth-session';
 import { withStore } from '@/lib/server/store';
 
 type Context = {
@@ -6,6 +7,12 @@ type Context = {
 };
 
 export async function DELETE(_request: Request, context: Context) {
+  const { session, response } = await requireAuthenticatedSession();
+  if (response) {
+    return response;
+  }
+
+  const userId = session.user.id;
   const { id } = await context.params;
   const numericId = Number(id);
 
@@ -16,7 +23,7 @@ export async function DELETE(_request: Request, context: Context) {
   let removed = false;
 
   await withStore((store) => {
-    const next = store.watchlist.filter((item) => item.id !== numericId);
+    const next = store.watchlist.filter((item) => !(item.id === numericId && item.user_id === userId));
     removed = next.length !== store.watchlist.length;
     store.watchlist = next;
   });